In image display devices, such as a cathode-ray tube display device (CRT), a plasma display panel (PDP), and a liquid crystal display device (LCD), anti-reflection films are generally provided on the outer surface of a display, so that reflectance can be reduced, using the principle of optical interference in order to prohibit reduction in contrast owing to reflection of external (ambient) light, and also not to mirror an image of a surrounding from being seen on the display surface.
Such an anti-reflection film can be prepared by forming a low-refractive-index layer having a proper thickness, on a high-refractive-index layer. The material of the low refractive index layer is preferably as low as possible in refractive index, from the viewpoint of anti-reflection performance. In addition, high resistance to abrasion (scratch) is demanded, because it is used on the outer surface of a display. Further, evenness in thickness of the film (coating) is also important, to attain low reflectance performance. Regarding the coating-type material, both excellent coating property and leveling property are also demanded as important factors.
To realize high resistance to abrasion in a thin film of about 100 nm in thickness, it is important to enhance both the mechanical strength of the coating and the adhesive property to a subbing layer. Known means for lowering the refractive index of the aforementioned material are such as (1) incorporation of a fluorine atom, and (2) reduction of density (incorporation of voids). However, a problem arises that the mechanical strength of the coating and the adhesive property are impaired by these means, which results in lowering of resistance to abrasion.
The resistance to abrasion is remarkably improved by imparting a sliding property to the surface, while keeping the refractive index as low as possible. To impart the sliding property, such means as incorporating fluorine, and incorporating silicone, are effective. These means, which can reduce surface tension, are also expected to impart a leveling property, which is another target to improve. When a low refractive index layer contains a fluorine-containing polymer, the low refractive index layer itself has a sliding property. However, it is difficult to obtain a satisfactory sliding property by the single use of a fluorine-based material having a short side chain in which about 50 mass % of a hydrocarbon-based copolymer component is incorporated, to impart solubility to a solvent. Therefore, the fluorine-based material has hitherto been used in combination with a silicone compound.
Addition of a small amount of a silicone compound to the materials of a low refractive index layer remarkably improves both the sliding property and resistance to abrasion. Further, in addition to the sliding property, such effects as water repellency and an anti-stain (anti-fouling) property are also obtained. However, on the other hand, the addition of a silicone compound causes various problems related to compatibility with the materials of a low refractive index layer (related to transparency of the coating); bleeding out with the lapse of time or under a condition of high temperature; transfer of a silicone component to a contact medium, and both deterioration of the performance and contamination of production lines due to these problems. Particularly in the anti-reflection film, formation of haze, due to insufficiency in compatibility, is a serious problem, because it impairs optical performance. Further, when a film after coating is rolled, adhesion of silicone to a back surface of the coating constitutes an obstacle to a subsequent processing step, which results in a serious problem. In this situation, there is a need to develop a technology to effectively segregate only a silicone site on the surface of a low refractive index layer, while effectively anchoring the remaining site bonding to the silicone site in the coating of the low refractive index layer.
Regarding proposal for resolving these problems, JP-A-11-189621 (“JP-A” means an unexamined published Japanese patent application), JP-A-11-228631, and JP-A-2000-313709 disclose a fluorine-containing olefin copolymer having a polysiloxane block copolymerized component incorporated therein, using a silicone macroazo initiator, and its application to an anti-reflection film. This method remarkably improves both evenness and durability of the coating. However, to arbitrarily control the sliding property of a material, some operations during the production of fluorine-containing olefin copolymers are needed, such as increasing the amount of a silicone macroazo initiator. In the production of polysiloxane-incorporated fluorine-containing olefin copolymers, if the amount of the silicone macroazo initiator is increased to raise the content of polysiloxane component, isolation performance of the produced polymer, by means of reprecipitation, is lowered. In addition, elimination of the remaining initiator or a component formed by mutual radical-coupling of initiator species, becomes very difficult. Therefore, it is not always easy to control the incorporated amount of the polysiloxane component.
From the aforementioned situation, there is a need to develop a technology by which the incorporated amount of the silicone component can be arbitrarily controlled without impairing evenness of a coating of a low-refractive-index layer.